A construction crane lies on a street in downtown Manhattan in New York on February 5, 2016 (AFP Photo/Kena Betancur)

A giant crane crashed in New York's Tribeca neighborhood Friday, killing one person and injuring three others, two of whom were in serious condition, Mayor Bill de Blasio told reporters.

The crane's operators were in the process of lowering and securing it amid adverse weather conditions including heavy snow, when it collapsed lengthwise down Worth Street in lower Manhattan, he said.

Four buildings were damaged and the three people injured by falling debris as the accident unfolded at 0830 am (1330 GMT), the mayor said.

It was still unclear why the 565-foot (170-meter) crane fell, De Blasio said, explaining that a crew "had inspected the crane yesterday."

Several minutes prior to the accident, construction workers had been deployed to divert pedestrians and cars from the area.

"Thank God it was not worse," De Blasio said, adding that the precautions likely prevented a heavier toll in the area, which is filled with offices and sees heavy traffic during rush hour.

The crane was mounted on a mobile tracked vehicle that also overturned during the accident.

It was replacing generators and the air conditioning system on the roof of the "Western Union" art-deco brick building built in 1930.

An order had been given for the city's 376 mobile cranes and 43 fixed cranes to be put in a secure position, De Blasio said. The city's last serious crane accident occurred in 2008, he added.

The crane belongs to the Bay Crane company and was being operated by Galasso Trucking and Rigging.

Giant crane falls in New York, killing one: official